In mounting ceiling or floor joists on headers, it is common to use metallic joist hangers. Such a hanger includes a U-shaped body comprised of a pair of side legs and a bottom web interconnecting the lower ends of the legs. Each leg of the hanger has a pair of mutually perpendicular parts, one part adapted to be nailed or otherwise affixed to the header and the other part adapted to be nailed or otherwise affixed to the side of the joist to be hung.
Generally, the hangers for a number of joists are mounted one by one after numerous measurements have been made on the header to provide alignment marks for the hangers. This procedure is time consuming and quite tedious where a large number of joist hangers are to be put into place. This represents a high labor cost, and such cost is to be reduced if at all possible. A need, therefore, has existed for some time for a tool which can be used to mount joist hangers in a minimum of time and with a minimum expenditure of effort. The present invention satisfies this need.